Thanks Andreas for the OGR suggestion and clarification on
ows_updatesequence.
There was a tantalising sentence in
https://agile-online.org/Conference_Paper/CDs/agile_2012/proceedings/papers/Paper_Loechel_Caching_techniques_for_high-performance_Web_Map_Services_2012.pdf
- with no space or links to the techniques to solve the problem!
" The purge effect leads to the problem, that a cache or mapserver might
respond outdated maps. This is assumed to be critical in two cases:
1. Manually changing data: The map has to reflect the change
immediately; otherwise users get confused and try to perform the change
again.
2. Automatically changing data: public map layers with up to date
information, like traffic conditions or weather data. There are special
techniques to solve this problem, but these cannot be explained in
detail here due to space limitations."
I'm rethinking the design of my application to workaround it, and can
think of 3 possible options:
1. Cache higher zoom levels, and switch to dynamic WMS at higher scales
as edits are normally made when zoomed in
2. The application has a log in function, so I could switch to dynamic
for users with edit-rights, and use a cache for read-only users (which
would update nightly). This would solve the issue where a user makes an
edit and the layer doesn't change.
3. Try and edit the XML MapCache config file and update a dimension to
cause a new cache to be generated following an edit. This approach would
probably lead to race conditions, and would need to be reloaded in Apache.
Regards,
Seth
On 04/10/2016 15:44, Eichner, Andreas - SID wrote:
Seth,
you can use OGR to retrieve the updated features and give it to mapcache_seed.
See
http://mapserver.org/mapcache/seed.html#optional-commandline-options-when-using-ogr-geos
.
The ows_updatesequence metadata signals changes in the metadata returned by a
GetCapabilities request, i.e. when adding/removing layers, descriptions and the
like.
HTH
-----Ursprüngliche Nachricht-----
Von: mapserver-users [mailto:[email protected]] Im
Auftrag von Seth G
Gesendet: Sonntag, 2. Oktober 2016 15:23
An: [email protected]
Betreff: [mapserver-users] Updating MapCache on feature edits
Hi list,
I have a few MapServer layers based on data that can be edited at any
time. In practice this usually happens in short bursts every month or so.
The remaining time the layers would benefit greatly from using a tile
cache.
Are there any suggested methods on how to automatically
purge/delete/change the cache when an edit happens when using MapServer
and Mapcache?
I see that GeoWebCache/Geoserver allows a GeoRSS feed to invalidate
features
http://geowebcache.org/docs/current/configuration/layers/georss.html
The ows_updatesequence metadata parameter for a WMS layer looks like it
could be used somehow (see http://mapserver.org/ogc/wms_server.html#web-
object-metadata), but it seems that custom dimensions need to be requested
by the client, and any Mapcache configurations would need Apache to be
restarted.
Any best practices, or solutions appreciated,
Seth
--
web: http://geographika.co.uk <http://geographika.co.uk>
twitter: @geographika
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